So, I calculated it and got appx: -26
I must be missing something, because I really do not know how to proceed from here...
I know how to use unit circle, but what is value of x, when sinx=-26?? Mr F says: No. x = -26, not sinx.

I am veeery confused now....

sin is negative in the 3rd and 4th quadrants. Using degrees, in the 4th quadrant, x = -26 + (360)n. In the 3rd quadrant, x = (180 + 26) + (360)n by symmetry of the unit circle.